The recirculation of flue gases is a technology which can basically be used for the most diverse purposes in gas turbines. Thus, flue gas recirculation is proposed, for example, for the reduction of NOx emission or for a reduction of the flue gas flow which is to be discharged. During the recirculation of flue gases in a gas turbine, a significant proportion of the flue gas is branched from the overall flue gas flow and, after being cooled and scrubbed, may be fed to the intake mass flow of the gas turbine or to the compressor. The recycled flue gas flow is mixed with fresh ambient air, and this mixture is then fed to the compressor.
As a result of flue gas recirculation, the carbon dioxide partial pressure in the flue gases can advantageously be increased in order to reduce the power losses and efficiency losses of power plants with carbon dioxide separation. In addition, flue gas recirculation has been proposed with the aim of reducing the oxygen concentration in the intake gases of gas turbines in order to reduce the NOx emissions as a result.
For flue gas recirculation, U.S. Pat. No. 7,536,252 B1, for example, describes a method for controlling a flue gas recirculation flow of a turbomachine, which is recycled, via a flue gas recirculation system, to the intake of the turbomachine. In this method, a setpoint flue gas recirculation ratio is determined, wherein the flue gas recirculation ratio is defined as a ratio of the flue gas flow to the intake flow of the turbomachine, and the actual value is adjusted to the setpoint value.
A method for operating a gas turbine with flue gas recirculation is known from U.S. 2009/0145126, in which the flue gas composition is determined, and by a control element a controlling of the flue gas recirculation is carried out as a function of the measured flue gas composition.
Also, if known techniques separating of condensates is specified after recooling, the mixing of recooled recirculated flue gas with fresh ambient air can lead to renewed condensation and forming of drops. Depending upon ambient conditions, for example, temperature and relative air humidity of the inducted ambient air, and operating state of the gas turbine, a significant forming of drops can occur during this mixing. These drops can find their way into the compressor along with the inducted flow and lead to erosion damage.